Condensation of iso-humulone in solution and at hydrophobic surfaces

Iso-humulone is an essential component for beer derived from hop, which is able to improve foam stability, increase bitterness and prolong shelf life, but its physiochemical properties have not been fully characterised. There is a limited amount of knowledge on how iso-humulone behaves in solution and at interfaces. In this work, the properties of iso-humulone are characterised in solution and at hydrophobic surfaces. The results show that iso-humulone is able to self-associate both in bulk solution and at the interface. The presence of ions typically found in beer (the mixture of Ca²⁺, K⁺, Mg²⁺ and Na⁺) increases the aggregation and adsorbed mass at the interface. Cryo-TEM confirms the presence of a liquid-like phase with nano-droplets with diameters of 20−90 nm. The results suggest that the droplets are spontaneously formed, have a limited growth through Ostwald ripening and can be dissolved upon dilution.